The amplitude and duration of the signals conveyed by the cyclic nucleotide second messengers, camp and cGMP, are controlled by their relative rates of synthesis and degradation. For many years now our laboratory has worked to understand the regulation of cyclic nucleotide degradation by phosphodiesterases (PDEs). Each animal species produce many different PDEs. To date 11 different PDE gene families have been identified most of which contain multiple genes each of which produce several different isozymes by the processes of alternative splicing of mRNA. We and others have made good progress in determining the physiological functions for some of these variant isozymes. It is the hypothesis of this proposal that many more PDE mRNA/isozyme variants remain to be identified and that until we do so, we cannot really understand the details of cyclic nucleotide mediated regulation of physiological processes. We propose an approach involving, bioinformatic searches, gene array identification, and standard methods of molecular biology and enzymology to identify, verify, clone, express, and characterize these new PDEs. We also propose to continue to determine functions for individual PDEs by characterizing the phenotypes of animals (and cells derived from these animals) that have specific disruptions of the genes encoding a particular PDE isozyme. As part of this second approach we propose to utilize a new methodology that is expected to allow conditional, reversible, tissue specific ablation of individual PDE expression. The methods make use of specific antisense and siRNA expression under the graded control of drug inducible promoters.